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2019/04/22 [General] UID:1000 Activity:popular
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 2009/3/29-4/3 [Computer/HW/Laptop, Science/GlobalWarming] UID:52768 Activity:high 3/29 "Leaving computers on overnight = $2.8 billion a year" http://tech.yahoo.com/blogs/null/130078 \_ Not good for hardware to power it up and down all the time. I always leave all my computers on all the time, except for laptops which I allow to sleep (but still be powered). \_ How is this the case for desktops but not laptops? I don't see ...  2007/10/5-9 [Reference/History/WW2/Germany] UID:48248 Activity:moderate 10/5 Although each D-Day landing craft had a 2 men assigned as flamethrowers, most of them did not carry flamethrowers out of fear that they'd explode. I love the History Channel -not getting laid guy #3 \_ Hey get your own nickname! - the original not getting laid guy. \_ Sorry I changed my login to not getting laid #3. Maybe ...  2007/4/18-21 [Reference/Military] UID:46353 Activity:moderate 4/18 "If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun." (The Dali Lama - May 15, 2001, The Seattle Times), "Among the many misdeeds of the British rule in India, history will look upon the Act depriving a whole nation of arms as the blackest" (Mohandas K. Gandhi - The Story of My Experiments with Truth, Page 403, ... Cache (623 bytes)  en.wikipedia.org/wiki/Smoothbore projectile, which stabilizes it and prevents it from tumbling. Early firearms did not have rifling, and had to fire spherical projectiles, so the random tumbling impacted the accuracy as little as possible. density on the periphery, and a low projectile density in the interior. This is the exact opposite of the desired even distribution, with a fairly even number of pellets across a carefully expanding region. kinetic energy penetrator for information on how this works). With the fins for stability, rifling is no longer needed and in fact the spin imparted by rifling will degrade the accuracy of a finned projectile. Cache (5696 bytes)  csua.org/u/fc6 -> www.amazon.com/gp/product/0387968903/104-3751901-3166352?v=glance&n=283155 Books Editorial Reviews Book Description In this text, the author constructs the mathematical apparatus of classical mechanics from the beginning, examining all the basic problems in dynamics, including the theory of oscillations, the theory of rigid body motion, and the Hamiltonian formalism. This modern approch, based on the theory of the geometry of manifolds, distinguishes iteself from the traditional approach of standard textbooks. Geometrical considerations are emphasized throughout and include phase spaces and flows, vector fields, and Lie groups. The work includes a detailed discussion of qualitative methods of the theory of dynamical systems and of asymptotic methods like perturbation techniques, averaging, and adiabatic invariance. Language Notes Text: English (translation) Original Language: Russian Product Details * Hardcover: 509 pages * Publisher: Springer; learn more) First Sentence: In this chapter we write down the basic experimental facts which lie at the foundation of mechanics: Galileo's principle of relativity and Newton's differential equation. Not all the epsilon and deltas are spelled out, and yet the the proofs are nowhere short of rigorous. Besides, they convey insight and intuition: the opposite of Gallavotti's "the element of mechanics" (a very competent book, but obsessed with details). As all the great mathematicians, Arnold separates what's essential from what is not, what is interesting from what is pedantic. I used it (partially) as a second year undergraduate text, and the teacher stressed in the first class that "if you understand Arnold you know classical mechanics". My advice is: get a good grasp of differential geometry and topology and of the tools of the trade (mathematical analysis, ODEs, PDEs) before studying it. Otherwise it will be still readable, but will not be fully appreciated. Arnold and is equally illustrious, is another master of style and clarity. You may want to check his book on dynamical systems and his essays. However, I know of only one physicist who successully worked out all the missing steps and taught from this book. In my text I do not restrict the discussion of integrability/nonintegrability to Hamiltonian systems but include driven dissipative systems as well. Another strength of Arnol'd: his discussion of caustics, useful for the study of galaxy formation (as I later learned while doing work in cosmology). Also, I learned from Arnol'd that Poisson brackets are not restricted to canonical systems (see also my ch. I guess that every researcher in nonlinear dynamics should study Arnol'd's books, he's the 'alte Hasse' in the field. But judging from the first 10 pages, there is a lot of mathematical handwaving. In contrast, foundations of mechanics (hereafter FOM) is far superior in that it provides all the necessary background beyond calculus and linear algebra to the reader, and is logically consistent so far in my reading. I want to mention that there are certainly complete and excellent texts out there on functional analysis, differential geometry, and topology, but many texts include way more stuff than you would want to know. In particular, it is my humble opinion that once you get to a certain point of knowledgeability of a subject like algebraic topology, you have enough of a taste for it that to learn more of the subject would only help if you were to go into research. Therefore a book like FOM provides a concise and practical treatment of those various advanced mathematics topics. Extremely clear if one has enough patience to follow exactly the author's way and to work out the proposed stimulating problems. The first part does not make use of symplectic formalism but is also quite original and stimulating. Very useful if used with E ott (Chaos in Dynamical Systems) for studying nonlinear dynamics. See all my reviews Arnold shines for clarity, completeness and rigour. But, at the same time, he requires a remarkable intellectual effort on the part of the reader (at least a physicist or an engineer). Some readers might see this as a book of math rather than physics, but that would not be fair: Arnold always stresses the geometrical meaning and the physical intuition of what he states or demonstrates. You can take full advantage from the effort of reading this book only if you master a wide range of mathematical topics: essentially differential geometry, ODEs and PDEs and some topology. That's not always true for engineer or physics students at the beginning graduate level. For that kind of readers, Goldstein is a much better fit. On the other hand, the exercises, although not very numberous, are very well conceived and help a lot to deepen the comprehension of the text. Also, the order of the topics is linear and very effective from a didactic point of view. The exposition is clear, concise and always goes straight to the point. Thanks to these features, it is one of the most effective books for self-teaching I ever happened to read. From a physical point of view, the domain of applications is essentially limited to discrete systems. Furthermore, the electromagnetism and relativity are not even cited, although they can be viewed as the logical completion of classical mechanics (see, for example, Goldstein). But the extreme generality of the approach largely balance the more restricted physical domain. In my opinion, the best book you can read on the topics. Suggestion Box Your comments can help make our site better for everyone. If you've found something incorrect, broken, or frustrating on this page, let us know so that we can improve it. Please note that we are unable to respond directly to suggestions made via this form. Cache (8192 bytes)  www.amazon.com/gp/product/0070037345/sr=8-2/qid=1143569740/ref=sr_1_2/103-6187066-5024642?%5Fencoding=UTF8 Books Editorial Reviews Book Description An outstanding volume in the McGraw-Hill series in pure and applied physics, Barger/ Olsson provides solid coverage of the principles of mechanics in a well-written, accessible style. Covering linear motion, energy conservation, Lagrange's Equations, Momentum Conservation and moving all the way through to Non-Linear Mechanics and Relativity, the text is comprehensive and appropriate for the two-semester course. Product Details * Hardcover: 384 pages * Publisher: McGraw-Hill Companies; The authors do however remain concrete in their treatment, with real-world examples permeating the text. The details behind the theory of classical mechanics are presented very quickly in the book, and this might make the book difficult to read for students first exposed to mechanics at this level. Chapter one is an introduction to motion in one dimension. After a brief review of Newton's laws, the authors solve some neat problems dealing with damping forces, one being the frictional force on a drag racer, and the other with aerodynamic drag on a parachute. They also treat the undamped and damped harmonic oscillator, and the discussion is very standard. The authors are careful to point out that some force laws are too complicated to be solved analytically, but that computing methods can be used to solve the cases that are not. Computational approaches are now the rule rather than the exception in problems in mechanics, and this trend will continue in the future. After a short discussion of energy conservation, the authors introduce motion in three dimensions and give a fairly detailed overview of vector notation. Their approach to tensors though is kind of antiquated, for it motivates them via the outer product, which is reminiscent of the dyadic approach that is currently "out of fashion". The authors also discuss the simple pendulum, but do not of course introduce the elliptic curve solutions that accompany this problem. Such a treatment, however fascinating, would drive this book to a height that would make it inaccessible to the audience of students it addresses. Coupled harmonic oscillators are solved using the normal mode approach. Lagrangian mechanics is introduced in chapter 3, but not from the standpoint of variational calculus at first. Instead the authors choose to present this formulation via generalized forces. They include a discussion of constraints, and give as an example the simple pendulum with a moving support. Only later do they give the Lagrangian formulation via variational calculus, and do so rather hurriedly. Hamilton's equations are derived, and it is shown (again briefly) how Legendre transformations enter into the formalism of Hamiltonian mechanics. Conservation principles are then thought of as fundamental in the rest of the book, and the authors use momentum conservation to discuss elastic and inelastic collisions in chapter 4 Angular momentum conservation is then used in chapter 5 to discuss central forces and planetary motion. Kepler's laws are also discussed, and Rutherford scattering is discussed. All of the discussion is pretty standard and can be found in most textbooks on classical mechanics. Rigid body mechanics makes its appearance in chapter 6, wherein the authors discuss the rotational equations of motion of many-particle systems and rigid bodies. A very brief discussion of gyroscopic mechanics is given, but the authors make up for this by explaining the motion of boomerangs. The discussion is fun to read and should satisfy the curious reader as to why a boomerang returns. And, after a discussion of how to calculate the moment of inertia, the authors give a neat introduction to the physics of billiards and the superball. The latter is a popular physics demonstration and the authors show how its motion differs from an ordinary smooth ball. The difficult (and controversial) topic of accelerated coordinate systems is treated in chapter 7 The four famous "fictitious" forces are introduced, and to develop the reader's intution on these, the authors give a nice example dealing with the manufacture of telescope mirrors. The casting of the mirrors is a neat illustration of the famous Newtonian water pail experiment. The motion of the Foucault pendulum is also discussed briefly. Then after a discussion of principal axes and Euler's equations, the authors give another neat example, this time dealing with the motion of tennis rackets, which illustrates the motion of a rigid body with unequal principal moments of inertia. The physics of tops is then discussed, and in a manner which makes the underlying physics more intuitive for the reader. The authors make an attempt to understand the motion of the famous tippie-top, but don't really do so. The tippie-top is another popular demonstration in the classroom but its physics has eluded the best attempts, and this treatment is no exception. The flip times that are calculated are not in agreement at all with what is observed in the demonstration. Chapter 8 is an overview of gravitational physics, and the authors show the effects of a body moving in a non-uniform gravitational field, with an example dealing with the tides. Interestingly, the authors attempt to introduce the general theory of relativity, and do so more at a level of elementary mathematics and arm-waving arguments, but the treatment is suitable at this level. The authors show the difference between the orbits predicted by general relativity and the Newtonian theory, ie the famous perihelion advance. A brief overview of Newtonian cosmology is given in chapter 9, wherein the authors discuss the expansion of the universe and the cosmic redshift. After proving the virial theorem, they discuss the effects of dark matter on the rotations of spiral galaxies and groups of galaxies, which is currently a very hot topic in astrophysics. The special theory of relativity is treated in chapter 10, and the discussion is very standard. Readers are introduced to relativistic mechanics and some of the counterintuitive physics of the theory. The last chapter of the book is an introduction to non-linear dynamics and chaos. It is defined as sensitive dependence on initial conditions, although this is not a strong enough condition. The Duffing oscillator is offered as an example of chaotic behavior and the transition to chaos is studied as a function of the driving frequency. This brings up concepts from bifurcation theory, such as the idea of a strange attractor. Numerical analysis plays the dominant role in these theories. See all my reviews This book made me violently angry for the first semester, the lagrangian is presented well, and the Foucault Pendulum is ok if it weren't for all the errors (not glaring missing d/dt in a couple places, if you know the material you pick it out quickly). I did learn well because of the torture of surviving my CM class, the problems sets are pretty neat I will say, but vague at times and a HUGE array of difficulties, from "what's 2+2?" to problems that made me nauseous, and produced intantaneous narcolepsy. In hindsight I learned quite a bit and its a neat litle hand book for the Grad, but man its painful for the new student. this is a tensor" is ridiculous, a math appendix would do WONDERS, or having the Feynman lectures nearby as well. I'd say with some better editing and some more appendecies it would be a good book, beware though the book is TINY and the price is meaty. Needs more examples, August 31, 1999 Reviewer: A reader I had studied "Classical Dynamics" by Marion more than 25 years ago. At the time I found Marion to be a difficult leap from the relatively easy first courses. Most of the critism, I suspect, comes from hitting the cold water for the first time. I thought the authors did a good job of explaining the concepts I wanted to review. I do not know how I would have felt if this were a first reading as my textbook 25 years ago. The one suggestion I can make is a plea for more example problems worked in detail. Like most physics students, problem solving is the most difficult task to master and seeing the techniques used by the masters are not to ... Cache (108 bytes)  csua.org/u/ahe -> www.amazon.com/exec/obidos/tg/listmania/list-browse/-/ZA7JFX4FTDKP/ref=cm_lm_lists/002-3858459-5085603 The claim on t he back that this is an undergraduate textbook should not be taken serio usly outside Russia. Cache (2106 bytes)  farside.ph.utexas.edu/teaching/336k/lectures/node74.html Gyroscopic precession Rotational stability Consider a rigid body for which all of the principal moments of inertia are distinct. Suppose that the body is freely rotating about one of its principal axes. Let the body be initially rotating about the$x'$-axis, so that \begin{displaymath} \mbox{\boldmath$\omega$} = \omega_{x'}\,{\bf e}_{x'}. Since the term in square brackets in the above equation is positive, the equation takes the form of a simple harmonic equation, and, thus, has the bounded solution: \begin{displaymath} \lambda = \lambda_0 \,\cos({\mit\Omega}_{x'}\,t - \alpha). It follows that the body is stable to small perturbations when rotating about the$x'$-axis, in the sense that the amplitude of such perturbations does not grow in time. Suppose that the body is initially rotating about the$z'$-axis, and is subject to a small perturbation. A similar argument to the above allows us to conclude that the body oscillates sinusoidally about its initial state with angular frequency \begin{displaymath} {\mit\Omega}_{z'} = \left \frac{(I_{z'z'}-I_{x'x'})\,(I_{z'z'}-I_{y'y'})}{I_{x'x'}\,I_{y'y '}}\right ^{1/2}\! Suppose, finally, that the body is initially rotating about the$y'$-axis, and is subject to a small perturbation, such that \begin{displaymath} \mbox{\boldmath$\omega$} = \lambda\,{\bf e}_{x'} + \omega_{y'}\,{\bf e}_{y'} + \mu\,{\bf e}_{z'}. Hence, the above equation is not the simple harmonic equation. Indeed its solution takes the form \begin{displaymath} \lambda = A\,{\rm e}^{\,k\,t} + B\,{\rm e}^{-k\,t}. Hence, the body is unstable to small perturbations when rotating about the$y'\$ -axis. In conclusion, a rigid body with three distinct principal moments of inertia is stable to small perturbations when rotating about the principal axes with the largest and smallest moments, but is unstable when rotating about the axis with the intermediate moment. Finally, if two of the principal moments are the same then it can be shown that the body is only stable to small perturbations when rotating about the principal axis whose moment is distinct from the other two.